Ethekwini Municipality recently approved the rehabilitation of the KwaMashu Waste Water Treatment Works situated about 25kms north of Durban. Aecom Consulting Engineers specified half a dozen Sika products which were applied in three separate phases of the project.

The first application of Sika products involved waterproofing the roof slabs which measured approximately 900m2. Contractor, Industrial Linings Natal, prepared the surface area by grinding and pressure cleaning, prior to an application of Sikalastic-EP Primer II (no quantity), a two-part, low viscosity, epoxy-polyamine resin. This multi-purpose primer is easy to apply, with short waiting times, and provides good penetration and high bond strength. It is suitable for internal and external use and can be used as a primer for all PUR and polyurea systems.

This was followed by a 1.5mm layer of Sikalastic-841 ST (no quantity), a two-part, very fast-curing pure polyurea membrane designed for machine application only. This versatile product is suitable for waterproofing and anticorrosion applications on concrete, steel and many other substrates. It is 100% solids with zero VOC, is UV resistant and provides excellent crack-bridging properties.

The second application of Sika products for strengthening of the roof slabs was awarded to AMFRA Maintenance Services. After diamond grinding the roof surface, a preparation layer of Sikadur-30 (8 kits) was applied. Based on a combination of epoxy resins and special filler, this structural two-part adhesive is easy to mix and apply and offers high creep resistance under permanent load. The shrinkage-free hardening of Sikadur-30 is not affected by high humidity, a significant factor for this particular project. It provides high initial and ultimate mechanical resistance and is impermeable to liquids and water vapour.

To complete this phase, a layer of Sika CarboDur Plates (S512 x 116 metres) was applied over the adhesive. These pultruded, carbon fibre reinforced polymer (CFRP) laminates are designed for external reinforcement of concrete, timber and masonry structures. This internationally approved product is used worldwide in a wide range of applications including load increase, damage to structural elements as in earth quake damage, service improvements such as stress reduction in steel reinforcement, as well as for changes to a structural system. Supplied in lightweight rolls, Sika CarboDur Plates are very easily installed, while their high strength and outstanding fatigue resistance provide excellent durability.

The third and final stage of the project involved joint sealing on the five Digester Tanks. Fakazi Construction applied 80m x 2mm of the Sikadur-Combiflex SG system, which consists of a modified flexible Polyolefin (FPO) waterproofing tape with advanced adhesion, to each tank.

The tank surfaces were prepared by scabbling, prior to a coating of Sikadur-31 CF Normal, a moisture-tolerant, thixotropic, structural two-part adhesive based on a combination of epoxy resins and special fillers. This high strength adhesive and repair mortar offers very good chemical resistance.

When fixed to a joint, the versatile Sikadur-Combiflex SG sealing system allows for irregular and high movement in more than one direction, whilst still maintaining a high quality seal. It is easy to install, extremely flexible, weather- and water-resistant and is suitable for use in many difficult situations.

The main contractor on this project, Icon Construction, coordinated the three sub-contractors so that each Sika application was done according to a scheduled programme for 2013. After receiving the best possible rehabilitation possible, the KwaMashu Waste Water Treatment Works should be structurally sound far into the foreseeable future.